I have configured VPN (PPTP) connection (configured as in screenshot) and I'm experiencing this issue (ubuntu 12.10):
The connection works fine, I can browse web and access local content, however after sometime it freeze ( also ping a local address doesn't give answer anymore ) and the only way to re-enable the connection is to stop it and restart it
UPDATE:
I have noticed in var/log/syslog that when the connection freezes the system starts to log these messages:
pppd[8268]: Protocol-Reject for unsupported protocol 'IP6 Header Compression' (0x4f)
pppd[8268]: Protocol-Reject for unsupported protocol 0x1c18
pppd[8268]: Protocol-Reject for unsupported protocol 0xb9
pppd[8268]: Protocol-Reject for unsupported protocol 'RTP IPHC Full Header' (0x61)
pppd[8268]: Protocol-Reject for unsupported protocol 'KNX Bridging Control Protocol'
The issue looks like this one:
http://newsgroups.derkeiler.com/Archive/Comp/comp.protocols.ppp/2007-01/msg00010.html
Settings :
